5 maximum values in a python dictionary

Question

I have a dictionary like this:

A = {'a':10, 'b':843, 'c': 39,.....} 

I want to get the 5 maximum values of this dict and store a new dict with this. To get the maximum value I did:

max(A.iteritems(), key=operator.itemgetter(1))[0:] 

Perhaps it is an easy task, but I am stuck on it for a long time. Please help!!!

Answer 1

No need to use iteritems and itemgetter. The dict's own get method works fine.

max(A, key=A.get) 

Similarly for sorting:

sorted(A, key=A.get, reverse=True)[:5] 

Finally, if the dict size is unbounded, using a heap will eventually be faster than a full sort.

import heapq heapq.nlargest(5, A, key=A.get) 

For more information, have a look at the heapq documentation.

Answer 2

You are close. You can sort the list using sorted ^[docs] and take the first five elements:

newA = dict(sorted(A.iteritems(), key=operator.itemgetter(1), reverse=True)[:5]) 

See also: Python Sorting HowTo